import java.util.Scanner;

public class RunwayLength {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入起飞速度 v(m/s) 和加速度 a(m/s²)：");
        double v = input.nextDouble();
        double a = input.nextDouble();
        double length = (v * v) / (2 * a);
        System.out.printf("所需最短跑道长度为 %.3f 米%n", length);
        input.close();
    }
}